The outbreak of a novel H1N1 influenza in the spring of 2009 took epidemiologists, immunologists and vaccinologists by surprise and galvanized a massive worldwide effort to produce millions of vaccine doses to protect against this single influenza strain. The pandemic has been associated with a w-shaped age-related susceptibility curve, which was also observed during the 1918 pandemic. Because of the unique epidemiology of novel H1N1 influenza, we hypothesize that response to cross-conserved T cell epitopes might have contributed to diminished reports of influenza-like illnesses and confirmed novel H1N1 infection among older adults in the absence of cross-reactive humoral immunity. Our initial in silico analysis identified more than sixteen cross-conserved epitopes in the A/California/04/2009 (H1N1) sequence published in March 2009 and now we wish to take that study further with the assays described in this research plan. We therefore propose studies that evaluate the ability of highly conserved HA and NA T cell epitopes from circulating, seasonal H1N1 strains and the conventional trivalent influenza vaccine (TIV) to elicit robust and durable immune responses in humans and in a murine model. The aims for this project are to: (1) Synthesize and validate immunogenic consensus sequence cross-conserved influenza class II epitopes, using available influenza sequences as our point of departure, (2) Validate the ICS epitopes for their ability to bind relevant HLA molecules in HLA competition binding assays and evaluate the epitopes' antigenicity using peripheral blood leukocytes from TIV, seasonal influenza-exposed and novel H1N1-exposed human subjects. Finally, (3) evaluate their effect on immunogenicity and protective efficacy against novel H1N1 in the HLA transgenic mouse model when used to prime with/without flu vaccine, in collaboration with Dr. Richard Webby. We expect to find that antibody titers are higher and manifestations of influenza are attenuated in mice primed with the cross-reactive epitopes, compared to mice not primed. We expect the results of these studies to demonstrate that conserved influenza sequences, which are important to viral fitness, may also be of immunological value in that they may contribute to protection against morbidity and to universal influenza vaccine design, leading to re-evaluation of alternative approaches to priming influenza immune responses, attenuating illness and preparing for the next pandemic. PUBLIC HEALTH RELEVANCE: The unexpected emergence of swine-origin influenza virus in 2009 prompted vaccine developers to produce a vaccine specific for the novel strain. We will explore the potential for cross-strain immunogens to induce immune responses that may give rise to development of a universal influenza vaccine.